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Aug 21, 2014 | 01:01 AM

kylek95

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Cel...

So 1995 460
it runs great but the check engine light is coming on showing code 173 for running too rich. So far i have replaced the o2, replaced a vacum thing (cant think of the name of it right now) and i replaced the tps. This is where it gets kinda trickey...Runs great but even when i unplug the o2 and run it around about 15 minutes into driving the light still comes on for the code 173 so is there another sensor somewhere that picks up / caculates the richness? Thanks

Aug 21, 2014 | 01:02 AM

kylek95

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Oh and i forgot the fuel pressure is GOOD about 32psi at idle and 40i when you unplug vacum from the regulator.

Aug 21, 2014 | 01:09 AM

85e150

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WAG alert. T-stat issues, running too cold causing the EFI to stay in rich mode for warm up. Or temp sensor issues so it thinks it's cold but it ain't.

Aug 21, 2014 | 01:21 AM

kylek95

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Yep brand new 190 tsat and coolant temp sensor the needle sticks almost straight up on temp gague...any more ideas?

Aug 22, 2014 | 01:06 AM

kylek95

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SOMEBODY has had to have had this happen to then before????? The 173 code comes.on even when i clear the codes and run it around with the o2 unplugged. Anyone wanna take a stab at what it could be?

Aug 22, 2014 | 11:03 AM

85e150

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Was there an "event" after which all this started?

Have you checked your connections, making sure the voltage from the O2 sensor is being read?

Does it have EGR? Checked that?

Checked for vacuum leaks everywhere, especially manifold to heads?

You are correct, this is a common problem.

Rough idle and running very rich - FSB Forums

https://www.ford-trucks.com/forums/1...le-idle-2.html

IAC was a problem. Different year, not sure how that translates to your truck or if you have an idle air control.

Aug 22, 2014 | 11:12 AM

85e150

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Forget the above unless this doesn't work. Purge solinoid, read on:

https://www.ford-trucks.com/forums/1...172-173-a.html

Deeply analytical:

https://www.ford-trucks.com/forums/4...ivability.html

Fuel pressure regulator:

https://www.ford-trucks.com/forums/1...ease-help.html

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Aug 22, 2014 | 11:50 PM

85e150

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Scroll down to "... Diagnosis"

What the Home Mechanic Needs to Know about O2 Sensors

More of the same:

http://densoautoparts.com/sites/defa...ing%20tips.pdf

Short version, between 0 and .9 volts.

The sensor wires go into the engine computer. Might be hard to trace or follow them.